You might find it interesting to study the concept of limits from the right and limits from the left, which is a concept useful in the development of Calculus. For example, you have a function like
f(x) = 1 if x>0
f(x) = 0 if x=0
f(x) = -1 if x<0
limit of f(x) as x->0+ is defined as the limit of f(x) as x->0 from the right. This limit happens to be 1.
limit of f(x) as x->0- is defined as the limit of f(x) as x->0 from the left. This limit happens to be -1.
See also
Left and Right-Hand Limits.
+0 and -0 might also serve as useful notation for talking about very small nonzero numbers that are nonetheless close in a subjective sense to zero.
For example, 0.000000000000000000000000000000000000000000000001 is close to 0. Talking about +0 could be a way of talking about these numbers which are very close to zero but still positive.
Another way to use the notation of +0 and -0 is in certain variable types in programming that use a bit to denote + or - and the rest of the variable denotes a number (which could be 0). What -0 means in programming is whatever the progammer decides to use it for. Maybe the programmer will use -0 to denote NULL.
The concept of a negative counterpart is not without practical or theoretical utility. I would not say I've given an exhaustive exposition of the potential uses of these concepts.